Sutures are used to approximate, or bring together, tissue separated, for example, by some trauma, or wound or during a surgical procedure to close an incision or an organ perforation. Suturing instruments generally include a needle and a trailing length of suture material. In endoscopic procedures, the instruments placed through an instrument channel may include needles and sutures for stitching such a wound, incision or perforation within the patient's body cavity.
Physicians have often used endoscopes to examine, to biopsy, and to ablate the tissue of patients within lumens such as the esophagus and the bowel or other body cavity and internal patient sites. An endoscope generally includes either a rigid or flexible tube containing one or more optical fiber systems and, for operative uses (human or veterinary), one or more channels for passage of medical instruments. The optical system includes a light delivery system to illuminate the organ or site under inspection and a camera system to transmit the image of the site of interest to the viewer. The light source is normally outside the body and the light is typically directed via optical fiber bundles to the area of interest. The instrument channels and optical fiber bundles open into the body at the distal end of the endoscope and are generally parallel to the axis of the flexible endoscope.
A physician performing a therapeutic procedure with the use of an endoscope places flexible instruments through the instrument channels near the site within the body lumen or cavity where a procedure is to be performed while visualizing and illuminating an internal site using the optical fiber bundles.
More recently, a surgical technique known as natural orifice transenteric surgery (NOTES) is attracting interest. NOTES may be performed with an endoscope that is passed through a natural orifice, such as the patient's mouth, nose or anus, then through an internal incision in the stomach or colon, for example, thus avoiding any external incisions or scars. The NOTES technique has been used for diagnostic and therapeutic procedures in animal models, including transgastric (through the stomach) organ removal. Transcolonic approaches are also advocated for access to upper abdominal structures that may be more difficult to work with using a transgastric approach.
To minimize the trauma experienced by patients, both the number and diameter of the canula inserted into a patient should be minimized. When a procedure requires suturing tissue, a problem arises in the types of needles that can be delivered to the surgical site. Many surgeons prefer to use curved needles which are typically in the range of ¼ to ⅝ of a circle (i.e. an arc whose interior angle is in the range of about 90°-225°). Needles of these dimensions would require canula, or endoscope working channels, large enough to accommodate the arc of the needle, which in many procedures, is not feasible. The preferred curved surgical needles cannot pass through the preferred, narrower, canula to the surgical site.
In an effort to resolve the problem, alloys that display a shape memory effect, such as those having approximately 50 atomic % nickel (Ni) and 50 atomic % titanium (Ti), are now widely used. The shape memory effect is arises due to a phase change that takes place in certain alloys as they are cooled or heated through their characteristic transformation temperature. The best known shape memory alloys are Ni—Ti (Nitinol) alloys in which the phase change is from an ordered cubic crystal form above the transformation temperature to a crystalline phase below the transformation temperature. The transformation is known as a martensitic transformation between a high temperature “austenitic” form and a low temperature “martensitic” form. An alloy becomes martensitic over a narrow temperature range as it is cooled through its transformation temperature and becomes austenitic over a narrow and slightly higher temperature range as it is heated through its transformation temperature. For a given alloy composition in a given annealed condition, the transformation takes place at a predictable, repeatable temperature. The transformation takes place virtually instantaneously when the alloy in one phase reaches a temperature at which the other phase is thermodynamically more stable.
Shape memory alloys have been used for the manufacture of surgical needles wherein a surgical needle is fabricated from a shape memory alloy into the desired “arc” shape. The arc is maintained at a temperature well above the austenitic phase. The needle is then cooled, transforming the material to the martensitic phase. While in the martensitic phase, the needle is deformed (for example, straightened) to the extent necessary to be able to pass through a canula.
U.S. Pat. No. 4,926,860 discloses arthroscopic instrumentation that takes advantage of the “superelasticity” inherent in shape memory alloys. Similar technology is disclosed in U.S. Pat. No. 4,984,581. U.S. Pat. No. 5,597,378 describes a method of making a shape memory alloy canula.
U.S. Pat. No. 5,219,358 discloses a method for introducing a curved needle to a surgical site in a patient and comprises the steps of (a) inserting a canula into the patient to permit access form outside the patient to the surgical site, (b) providing a shape-metal-alloy needle that, having been formed into an arc shape and tempered at an elevated temperature, has been formed into an elongated shape while in a first, low-temperature state, (c) passing the elongated needle through the canula, and (d) heating the needle to a temperature at which the alloy is converted to a second, high-temperature state, thereby causing the needle to return to the arc shape. Heat can be provided, for example, by an illumination light, by a laser, or by a cautery instrument of any type used in endoscopic surgery. The needle is transformed to the austenitic phase and reverts to the curved shape. Thus, the alloy used for shape memory effect surgical needles preferably undergoes its phase transformation in a narrow range near normal body temperature. Since practical and medical reasons limit the temperature to which the needle can be heated at the surgical site, the alloy is preferably austenitic at a temperature slightly below body temperature, for example, at about 35° C. and above, or room temperature, about 25° C.
Advances in shape memory effect materials and the manufacture of curved needles with such materials makes the use of curved needles in endoscopic surgery possible. However, it has been found that in the process of puncturing a patient's tissue at an internal site through a canula or the working channel of an endoscope, there is a tendency for the tissue to shift. This is particularly true for tissues of the gastrointestinal tract. The pressure of the curved needle puncturing the tissue, first in one direction and then in a second opposite direction as the curve of the needle circles around back through the tissue, pulls at the tissue and causes it to shift, ripple or buckle, such that one or both of the first and second punctures of the curved needle are not in the desired location. A means of stabilizing the tissue while suturing with a curved needle is needed.